Direct detection of dark matter in models with a light Z'

TL;DR

This paper explores how a light Z' mediator can enable dark matter to produce detectable signals in direct detection experiments, reconciling conflicting experimental results through isospin violation and different interaction types.

Contribution

It demonstrates that a light Z' mediator with specific couplings can explain DAMA and CoGeNT signals while satisfying XENON100 bounds, highlighting the role of isospin violation.

Findings

Isospin violation with f_n/f_p = -0.7 can reconcile DAMA and CoGeNT with XENON100.

The Z' mediator can produce large spin-dependent cross-sections.

The model explains both spin-dependent and spin-independent signals in direct detection experiments.

Abstract

We discuss the direct detection signatures of dark matter interacting with nuclei via a Z' mediator, focussing on the case where both the dark matter and the $Z'$ have mass of a few GeV. Isospin violation (i.e. different couplings to protons and neutrons) arises naturally in this scenario. In particular it is possible to reconcile the preferred parameter regions inferred from the observed DAMA and CoGeNT modulations with the bounds from XENON100, which requires f_n/f_p = -0.7. Moreover, the Z' mediator can also yield a large spin-dependent cross-section which could contribute to the DAMA signal, while the spin-independent cross-section is adequate to explain the CoGeNT signal.